I don't think you can nest within the lstlisting environment. Since this is a verbatin environment, the second \begin{lstlisting} is ignored, and the first \end{lstlisting} results in the termination of the outer \begin{lstlisting} leaving an extra \end{lstlisting}.
If you provide more details on exactly what you want to do, perhaps we can provide a way to accomplish that.
If all you want to do is to show the LaTeX output using the listings environment, I'd use the showexpl package:

\documentclass{article}
\usepackage{xcolor}
\usepackage{listings}
\usepackage{showexpl}
\lstdefinestyle{demoLatexStyle}{
basicstyle=\small\ttfamily,
numbers=left, numberstyle=\tiny, stepnumber=2, numbersep=5pt,
frame=none,
basicstyle=\small\ttfamily,% print whole listing small
}
\lstloadlanguages{[LaTeX]TeX}
\begin{document}
\begin{LTXexample}[pos=b,style=demoLatexStyle]
\begin{lstlisting}
blah blah
\end{lstlisting}
\end{LTXexample}
\enddocument}